1. Field of the Invention
The invention relates to a magnetic resonance imaging method for following a dynamic process in a body, in which method a local modification of magnetic resonance properties is induced in the body to produce a selective variation of magnetic resonance signals to be generated in the body, magnetic resonance signals being acquired during, or during and after the realisation of the modification by way of a first signal acquisition method in order to form a series of magnetic resonance images of the body enabling the dynamic process to be followed.
2. Description of the Related Art
A magnetic resonance imaging method of this kind is known from the article "First-Pass Cardiac Perfusion: Evaluation with Ultrafast MR Imaging", D. J. Atkinson et at., Radiology, March 1990, pp. 757-762. The cited article describes cardiac perfusion where, in order to modify the magnetic resonance properties, the contrast agent Gd-DTPA (Gadolinium diethylenetriaminepentaacetic acid) is injected into a body via veins in conjunction with an MR imaging method whereby strongly T.sub.1 -weighted NMR images are obtained. The NMR signals are enhanced by the Gd-DTPA. The imaging method consists of a 180.degree. inversion pulse, followed by a gradient-echo signal acquisition method with very short repetition time (&lt;4 ms). Suitable contrast is achieved by choosing the inversion time, i.e. the period of time elapsing between the inversion pulse and the gradient echo signal acquisition methods, so that the NMR signal is zero for non-enhanced myocardium and non-zero for enhanced myocardium in the case of cardiac perfusion. A high temporal resolution is necessary for the following of such a fast process, or another fast process such as perfusion in the brain, i.e. the signal acquisition method should be very fast. A high temporal resolution is usually achieved at the expense of spatial resolution. In the case of cardiac perfusion reasonably high spatial resolution requirements can still be satisfied, be it that gated imaging over a plurality of heart beats is then required. However, for example in the brain where a temporal resolution in the order of one second is required, during the following of such processes it is difficult to achieve suitable spatial resolution when practically feasible signal acquisition methods are used. When use is made of a fast Fourier imaging method, acquisition of only 40 profiles in the phase encoding direction will be possible, giving rise to undiagnostic NMR images, even after interpolation to a larger data matrix.